1. Field of the Invention
The present invention relates to a solid-state imaging device, a method of manufacturing thereof, and an electronic apparatus.
2. Description of the Related Art
Electronic apparatuses such as a digital video camera and a digital still camera include solid-state imaging devices. For example, as the solid-state imaging device, a CMOS (Complementary Metal Oxide Semiconductor) type image sensor, a CCD (Charge Coupled Device) type image sensor, or the like is included.
In the solid-state imaging device, a plurality of pixels is arrayed in a matrix shape on an imaging area of a semiconductor substrate. Each pixel is provided with a photoelectric conversion portion. For example, photodiodes are disposed as the photoelectric conversion portions.
Among solid-state imaging devices, in the CMOS type image sensor, the pixel is configured to include semiconductor devices such as a pixel transistor other than the photoelectric conversion portion. With respect to the pixel transistors, a plurality of transistors are configured so as to read out signal charges generated by the photoelectric conversion portions and to output electric signals to signal lines.
In the solid-state imaging device, when photographing a color image, the photoelectric conversion portion generally receives light incident through color filters on a light-receiving plane and performs photoelectric conversion to generate the signal charges.
For example, the color filters of the three primary colors of red, green, and blue are disposed in a Bayer array on the imaging area, so that light of each color transmitting the color filter of each color is received by the photoelectric conversion portion in each pixel. In other words, by considering the pixel which the red color filter is disposed above, among the light incident as a subject image, the light of the green and blue components are absorbed and only the light of the red component transmits the red color filter, so that the transmitted red light is received by the photoelectric conversion portion disposed at the lower layer thereof.
Miniaturization of the solid-state imaging device and an increase in the number of pixels are necessary. Therefore, as the size of one pixel is further reduced, it is difficult to receive a sufficient light amount, and the image quality of the photographed image is not easily improved.
In order to solve these problems, a “lamination type” is proposed where the photoelectric conversion portions which selectively receive the light of the colors are not disposed in the direction parallel to the imaging area but the photoelectric conversion portions of the colors are disposed to be laminated in the direction perpendicular to the imaging area.
In the “lamination type”, for example, it is proposed that three layers of the organic photoelectric conversion layers are laminated as the photoelectric conversion portion so as to sequentially receive the three primary color light included in the incident light. In this case, a portion of the incident light is absorbed in the photoelectric conversion portion disposed in the upper portion so that the photoelectric conversion is performed. Then, a portion of the light which is not absorbed in the photoelectric conversion portion disposed in the upper portion is absorbed in another photoelectric conversion portion disposed in the lower portion so that the photoelectric conversion is performed. For example, the photoelectric conversion portion of the uppermost layer absorbs green light; the photoelectric conversion portion of the middle layer absorbs blue light; and the photoelectric conversion portion of the lowermost layer absorbs red light. In addition, in each photoelectric conversion portion, the photoelectric conversion is performed so that signal charges are generated (for example, refer to Japanese Unexamined Patent Application Publication No. 2005-347386).
Besides, in the “lamination type”, for example, it is proposed that a photoelectric conversion portion is disposed in an internal portion of the semiconductor substrate and an organic photoelectric conversion layer as a photoelectric conversion portion is disposed above thereof. For example, it is proposed that photodiodes receiving blue light and red light are formed at different depths in the semiconductor substrate and a photoelectric conversion layer receiving green light is formed on the surface of the semiconductor substrate (for example, refer to Japanese Unexamined Patent Application Publication Nos 2005-353626 and 2008-258474).
In this manner, in the “lamination type”, each pixel receives not only mono-colored light but also a plurality of colored light. Therefore, it is possible to improve the light usage efficiency, so that it is possible to easily implement miniaturization. For example, in the case where three organic photoelectric conversion layers are laminated to receive the three primary color light of red, green, and blue, since the light usage efficiency is increased by three times, the area per pixel may be reduced, for example, by ⅓ times. In addition, in the case of the “lamination type”, since a demosaic process is not necessary in comparison with the case where pixels are arrayed in a Bayer array, it is possible to suppress the occurrence of a false color.